The cryoglobulins are a family of immunogloblulins that persist in the serum, precipitate with cold temperature <37° C., and resolubilize when rewarmed [J-P. Brouet et al., Am. J. Med. 57, 755-788 (1974); M. Dolcher et al., Clin. Exptl. Immun. 96, 317-322 (1994)). Cryloglobulins precipitate at lower temperatures, a phenomenon known as cold precipitation. Cryoglublinemia is a disorder of cryloglobulin function characterized by a typical triad of clinical symptoms—purpura, weakness, and arthralgias—and by one or more organ pathologies: e.g., hepatitis, glomerulonephritis, peripheral neuropathy, skin ulcers and diffuse vasculitis.
Cryloglobulins are quite heterogeneous and behave differently with respect to precipitation, dissolution or—more importantly—the disorders they produce in different body tissues. The cryoprecipitation phenomenon is unique for each cryoglobulin, and depends on the intrinsic properties of the immunoglobulin, the protein environment, temperature and surrounding ionic concentrations. The cold precipitation characteristic of the cryloglobulins is quite variable between the different cryoglobulins: For example, type I cryoglobulins (which are rare) can precipitate rapidly within minutes at temperatures close to body temperature, while type III cryoglobulins (which are common) hardly precipitate even after a week at ˜4° C.
In vivo, cryoglobulins precipitate in the capillaries and small blood vessels probably where the skin can be subjected to a very low temperature, often causing cutaneous problems, e.g., purpura, vasculitis and skin ulcers. These complexes can be carried to other organs causing further complications such as nephropathy and neuropathy.
Many clinical laboratories visually examine cryoglobulins upon sample cooling. Visual examination can detect type I and II cryoglobulins, which are present mostly in 100-1000 mg/dL amounts. However, type III cryoglobulins, which constitute about half of all samples presented to a clinical laboratory, are present in small amounts 3-50 mg/dL. Such small amounts can not be detected easily by visual examination.
Two works attempted to speed up the analysis mainly for screening purposes based on turbidity or nephelometry of the early stages of the precipitation (A. Kalovidouris and R. Johnson, Ann. Rheum. Dis. 37, 444-448 (1978); L. Yang et al., Pediatr. Res. 14, 858-862 (1980)). However, these techniques are not useful for quantitation or phenotyping. Other workers attempted to increase the amount of precipitation while keeping the samples cold for the 5 days analysis time. Accordingly, there is a need for new techniques for the rapid precipitation and analysis of cryoglobulins, particularly type III cryoglobulins.